1. Field of the Invention
The present invention relates to a flow control device capable of switching supply of fluid flow, mainly liquid. More specifically, it relates to a flow control device capable of accurately controlling flow with a simple arrangement.
2. Description of Related Art
A liquid medicine injection apparatus, for instance, uses a tube with small diameter having conduit function and flow rate control function and the liquid medicine is supplied to the tube so that it is continuously injected into human body little by little.
Conventionally, flow rate of the liquid medicine injection apparatus having the conduit function and the flow rate control function is changed by exchanging the tube, which makes it impossible to change the flow rate immediately.
On the other hand, a device disclosed in Japanese Patent Application Laid-Open Publication No. Hei 5-84310 is known as a flow control device adapted for continuously injecting small amount of liquid medicine and capable of adjusting flow rate in a multistage.
The above device has a body including a cylindrical hollow valve chest in communication with the outside through an inflow hole and at least three outflow hole, and a plug body including a cylindrical valve portion rotatably accommodated in the valve chest, the valve portion provided with a slit opened in fan-shape and a straight-tube thin hole extending from a base portion of the slit to the radially opposite side, the fan-shaped slit being connected to the inflow hole when the thin hole is connected to either one of the outflow holes.
However, in the conventional arrangement, since the flow is switched by bringing the thin hole coincident with the either one of the outflow holes, when there is a gap between the thin hole and the outflow hole, the fluid can leak therefrom. Accordingly, inner diameter of the valve chest and the outer diameter of the valve portion have to be strictly sized, thus requiring processing accuracy and much production cost.
A seal member may be interposed between the thin hole and the outflow hole to alleviate the problem. However, rotation resistance of the valve portion can be increased, so that the rotation of the valve body can be deteriorated, thus making it difficult to control the flow rate easily and accurately.
An object of the present invention is to provide a flow control device being capable of overcoming the above-described conventional disadvantage, having a simple structure and being produced by a simple process, and being capable of easily and accurately controlling the flow rate.
The present invention is a flow control device, having a body, a plurality of elastic flow control tube provided inside the body, a slide member slidable relative to the body, and a valve mechanism for selectively pressing and shutting the flow control tube in accordance with a slide position of the slide member.
According to the above arrangement, when the slide member is slid, the plurality of flow control tube is selectively pressed and shut in accordance with the slide position of the slide member. As a result, the fluid is supplied through a flow control tube that is not pressed and shut, so that the flow rate can be controlled by selecting the flow control tube to be pressed and shut.
In this case, since the flow rate can be controlled only by selectively pressing and shutting the plurality of flow control tubes, the flow rate can be easily and accurately controlled as well as simplifying production process and structure thereof.
In the present invention, the valve mechanism may preferably include a stationary-side projection provided to the body to receive the respective flow control tubes, a plurality of press-piece provided in the body correspondingly to the respective flow control tube and displaceable in a direction to press the flow control tube toward the stationary-side projection, the plurality of press-piece having a movable-side projection at a position opposite to the stationary-side projection sandwiching the flow control tube and shifted longitudinally along the flow control tube relative to the stationary-side projection, and a cam provided to the slide member for selectively displacing the plurality of press-piece in accordance with the slide position of the slide member to press and shut a corresponding flow control tube.
According to the above arrangement, since the stationary-side projection provided to the body and the movable-side projection provided to the press-piece are shifted longitudinally along the flow control tube, when the press-piece is displaced by the cam to press the flow control tube, the flow control tube is shut by being sandwiched by the stationary-side projection and the movable-side projection in a shearing manner, so that the flow control tube can be securely pressed and shut with smaller force as compared to an arrangement where the stationary-side projection and the movable-side projection sandwich the flow control tube therebetween with the stationary-side projection and the movable-side projection located at corresponding position. Therefore, the flow rate can be more precisely controlled.
In the present invention, the stationary-side projection may preferably be provided at two longitudinally spaced locations along the flow control tube, and the movable-side projection may preferably be provided at two locations outside a position corresponding to the two stationary-side projections.
According to the above arrangement, since the press-piece presses the flow control tube with the two movable-side projections longitudinally spaced along the flow control tube, the press-piece can be displaced in a parallel attitude without being tilted. In other words, since the flow control tube is pressed and shut by the two stationary-side projections and the movable-side projections longitudinally spaced along the flow control tube, the flow control tube can be selectively pressed and shut more securely.
In the present invention, a positioning mechanism for locating the slide member at a position for the slide member to selectively press and shut the flow control tube may preferably be provided between the body and the slide member.
According to the above arrangement, since the slide member can be located at a position for selectively pressing and shutting the flow control tube, in other words, since the slide member can be retained at an adjusted position, adjusted flow rate can be stably continued.
In the present invention, a flow rate indication index may preferably be provided on the slide member, and a flow rate display may preferably be provided on the body for displaying a flow rate on a position corresponding to the flow rate indication index at respective positions of the slide member located by the positioning mechanism.
According to the above arrangement, since the current flow rate can be recognized by reading the flow rate shown on the flow rate display coinciding with the flow rate indication index provided on the slide member at the respective position located by the positioning mechanism, the adjustment can be simply and easily conducted.
In the present invention, the flow control device may preferably have a lock mechanism including a lock key capable of being inserted into and drawn off from the body, the lock key being drawn off from the body to lock a slide movement of the slide member, and the lock key being inserted to the body to allow the slide movement of the slide member.
According to the above arrangement, after the lock key is inserted to control the flow rate by sliding the slide member, the slide movement of the slide member can be locked by drawing off the lock key.
Accordingly, when the present invention is applied to, for instance, a liquid medicine injection apparatus for continuously injecting liquid medicine by a small amount, the lock key can be inserted by a doctor or a nurse to control the flow rate by sliding the slide member and the lock key can be drawn off, so that the security can be ensured since a patient cannot control the flow rate himself.